Electroexplosive devices (EED's) such as detonators and blasting caps are sensitive to electromagnetic radiation and electrostatic charges, and can be prematurely or inadvertently detonated by such radiation and charges. Squibs may also be classified as EED's, even though they may contain a pyrotechnic composition instead of an explosive. Regardless of whether a low explosive or a pyrotechnic compositon is used, the composition in the EED is energetic and the function is the same--to begin a very rapid energetic reaction on command.
A typical EED has a fine gauge bridgewire embedded in a chemical mixture that ignites when brought to a high temperature, the bridgewire being heated by passing a relatively small amount of direct current therethrough. Because so little energy is required to ignite an EED, it is very sensitive to high frequency radiation which may be readily induced into the input leads and then into the bridgewire. EED's are also known to be sensitive to transient or spurious signals, stray currents, and static charges.
Various methods have been used to alleviate misfiring caused by electromagnetic radiation. Prior art systems have included RF traps with inductive and capacitive components, ferrite beads and external capacitors, and bypass circuits using diode and capacitor combinations. However, such devices--having a plurality of discrete components--are relatively expensive, and many of the prior RF attenuation systems cannot be readily applied to existing EED's. In addition, prior attenuators have generally been unsuitable for commercial production because of the costs involved in producing the units.
While the applicants herein have successfully created a device which attenuates electromagnetic energy and separates components which provide protection from electrostatic energy, as disclosed in U.S. Pat. No. 4,378,738, several improvements have been made thereto. All previous attempts to protect against stray electrostatic energy have utilized separate specialized components in the EED. Such components add additional cost to the device, and require an additional amount of labor to install them thereon.
Another problem with conventional attenuation devices is in the amount of attenuation provided in proportion to the size of the attenuator. Prior art devices required the serial stacking of a plurality of "beads" (ferrite devices having a single aperture with a single straight longitudinal conductor therethrough), in order to produce the necessary amount of attenuation. The applicants' previous U.S. Pat. No. 4,378,738, helped reduce the overall length of the device by the use of a conductor which passes through the ferrite three times. However, additional attenuation may be desired in many instances where a greater safety margin is necessary, or where a relatively short length requirement limits the use of prior devices.
It is therefore a general object of the present invention to provide an improved broadband ferrite choke attenuator.
Another object of the present invention is to provide a broadband attenuator which will attenuate electromagnetic radiation and equalize electrostatic charges without additional accessory devices.
A further object of the present invention is to provide an attenuation device which provides attenuation power equal to prior art devices, but using a lesser longitudinal length.
Yet another object of the present invention is to provide an attenuator which may be utilized in connection with a variety of different devices.
These and other objects of the present invention will be readily apparent to those skilled in the art.